1. Field of the Invention
This invention is concerned with a mashing method with the aid of which remarkable savings can be attained in relation to the energy consumption required by the process. According to the invention, the basic method is the alternating use of reactors so that the released reactor steam is led into a parallel reactor to be used as a part of steaming of the grain charge. The same procedure is also performed with the steam from the other reactor, in other words it is led into the first reactor in its turn. 2. Description of the Prior Art
The use of grain as a raw material in alcohol production usually comprises the following procedures:
grain processing and grinding or crushing PA1 mash cooking of the floour or crushings PA1 fluidisation and sugaring of the starch PA1 sugar fermentation into alcohol PA1 alcohol distillation from the fermented wort PA1 handling and drying the distilling wastes for fodder.
Of the above mentioned process stages the amount of energy consumed in mash cooking is considerable and for this reason efforts have been made by various means to reduce this.
Thus far the method which has been recognised as the most economical is the so called spray condensation method in which the expanded steam is led into a container or several containers into which the raw mash going to cooking is sprayed. Part of the steam condenses into the mash whereupon the mash temperature and its moisture content are increased. With this method of mashing the energy consumption in continuous cooking is about 0.71 MJ per kilo of grain.
It has been demonstrated that by using a heat exchanger to utilize the heat of the boiled mash to heat that mash which is being fed in, the energy consumption in ideal conditions would only be about 0.14 MJ per kilo of grain. The only extra energy requirement would then be needed for compensation of heat losses. For natural reasons it has not been possible to create this kind of circumstances. The pressure losses and fouling of heat exchangers lead to the actual energy consumption being noticeably larger.
The large amount of heat used in mashing methods is related to the large water content in the mash which makes the efficient utilisation of heat difficult. The grain to water ratio is commonly between 1:3.5 and 1:4. It is natural, then, that a reduction in water content in the mash would be advantageous when lowering energy consumption. A limitation to the reduction of the water content is however set, in that if too little water is used neither flour or crushings yield more than a tough putty-like substance the further processing of which is exceedingly difficult if not impossible.